Recently, the increasing concern over global environmental problems has seen the use of various kinds of fuel cells in automobiles coming under consideration. For example, in the case of a solid oxide fuel cell which is high in power generation efficiency, electric power is generated by an electrical chemical reaction between an anode gas containing, for example, hydrogen and hydrocarbons and a cathode gas containing oxygen.
JP2005-179081A discloses a fuel cell system that includes an anode discharge passage through which an anode off-gas discharged from a solid oxide fuel cell flows, a cathode discharge passage through which a cathode off-gas discharged from the solid oxide fuel cell flows, and a joining portion where these passages join. The anode off-gas and the cathode off-gas are combusted by a burner in the joining portion and then discharged outside the fuel cell system.